<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
		<script type="text/javascript">
			var xiaoming = parseInt(prompt("请输入小明的成绩")) ;
			var xiaogang = parseInt(prompt("请输入小刚的成绩")) ;
			var xiaohong = parseInt(prompt("请输入小红的成绩")) ;
			var avg=(xiaogang+xiaohong+xiaoming)/3;
			alert(avg);
		</script>
	</body>
</html>
